Bonjour Olivier, hello Rudi and Scott,
I want to add my observations of some years: The zinc anode of the Spurs line cutter is completely away after a year, if you do not have the zinc anode on the nose of (in my case folding) propeller. This means, the protection of the big 2 anodes on the rudder blade is most seemingly not enough to protect the line cutter (and the propeller I believe) from corrosion.
After installing the zinc anode on the propeller (instead of the 'red nose plastic' - as Olivier says), which by the way is quite easy also in diving, I detect no corrosion anymore at the zinc anode of the Spurs line cutter.
I am happy now with a full set of zinc anodes from bow to aft, on (1) the bow thruster, (2) the Onan Generator, (3) the spurs line cutter, (4) the nose of the Propeller and (5) the 2 big ones at the rudder blade.
This should last and avoid any corrosion easily a year!
Alexander Hofmann, SY Oceanica I, Amel 54#156